yeha, the origin of O-Ren wouldn't be first because the Bride is narrating that scene.
Same thing with Pai Mei chapter, its in that spot because its vital to what happens with Uma in the coffin. That whole coffin scene builds up and we're left thinking, "What is she gonna do?!" Then we go to PAi Mei and we're like, "Whoa, whats this?" and then we go back to The Bride busting out. If we never cut to the Pai Mei scene the buried alive sequence would'nt be as exciting and full of suspense, plus that scene is almost like a flashback.